The present invention relates to computer driven printers and, more particularly, to increasing the capacity of print media supply for an inkjet printer. For ease of reference, instead of the term print media, the term paper will be used herein and is intended to encompass all forms of print media including paper, transparencies, vellum, etc. One example of prior art printer with which the present invention is useful is the Hewlett Packard inkjet color printer Model 1200 which has standard vertically spaced paper input and output trays on the front of the printer as shown and claimed in co-pending application Ser. No. 08/055,650 filed Apr. 30, 1993 and assigned to the assignee of the present invention.
The standard paper input tray shipped with the printer has a capacity of about 180 sheets of paper resulting in frequent print stoppage for replenishment of the paper supply in the input tray during high volume printing. It is desired to reduce the amount of printer downtime due to reloading of the input tray.
Ordinary paper trays comprise rectangular bins having vertical walls with multiple springs and pressure plates to urge the stack of paper upwardly against drive rollers to permit reliable paper feeding. Another type of tray, particularly useful with the present invention, has a slanted wall at the paper output end which is designed to permit the surface tension of the paper in the tray to be broken with the paper being physically stacked in the tray at an angle as disclosed in U.S. Pat. No. 5,377,969, and owned by BDT Buero Datentechnik GmbH. Trays of this type employ an articulated paper pusher arm mounted in either the paper tray or the printer housing which urges the top sheet of paper in the tray toward the printer paper feed mechanism.
Also, as is well known, inkjet printers apply wet ink to the paper or other print medium which is preheated before application of the ink to prevent or at least minimize shrink banding of the paper. Accordingly, the HP 1600C color inkjet printer referred to above incorporates a paper pre-heater in the path of movement of the paper from the standard input tray, the pre-heater being located immediately before the paper reaches the print zone.
A primary objective of the present invention is to efficiently guide and transport paper from a relatively large capacity (as compared with the standard input tray) auxiliary paper input tray to the print zone of known printers without substantial modification of the printer design.
A second objective of the present invention is to use a portion of the known printer's paper transport and guide means in the paper transport path which extends from an existing manual single sheet paper feed input slot to the print zone to guide the paper to the print zone.
A third objective is to preheat paper fed from an auxiliary paper tray at a location proximate the print zone.